Gilmário Barbosa dos Santos

Visual evaluation of the length of artificially generated electrical discharges by 3D-snakes

The secondary arc extinction is the main concern in single-phase auto reclosure (SPAR) switching studies, since it dictates whether the reclosure will be successful or not. In this context, a function that describes the arc length variation over time (l(t)) is an important information not only for dynamic response but also for the analysis of transient arc processes. Given that purely electrotechnical approach only gives a profile of the curve l(t), the application of techniques based on image analysis has been considered for obtaining such function. In this paper, a new approach based on 3D-reconstruction and the tracking of an electrical arc is proposed for performing a computer-based evaluation of variations in its length. It was applied a three-dimensional active contour named 3D-snake that is geometrically represented by a B-spline, which evolves in 3D space. This new model is much less dependent on the determination of homologous points than the ad hoc approaches found in the literature for recovering 3D geometry of electrical discharges based on image analysis. In addition, the proposal presented is capable of tracking the evolution of the electrical discharge taking into account the time dependence between consecutive pairs of frames in two videos providing the required function l(t).

Maps of distances for evaluating the tracking and measurement of electrical arcs by 3D-snake

This paper presents a 3D reconstruction (by 3D-snake) of the longitudinal axis of an electrical arc (discharge) in evolution based on stereo pairs of images. The accuracy of such tracking depends strongly on the halting of the iterative relaxation process that adjusts the 3D-snake. The key aspect to make such decision is detecting when each projection of the 3D-snake matches special features in the pair of images. For this sake, this paper proposes a simple and effective strategy based on the projection matrices of the cameras and tables named Maps of Distances (MDs) which are obtained by image processing.

Snake-3D na Modelagem Tridimensional e Medição do Comprimento de Arcos Elétricos

Nesse trabalho e descrita a aplicacao inedita de um contorno ativo tridimensional (snake-3D) na avaliacao do comprimento de arcos eletricos artificialmente gerados em torres de alta tensao e capturados atraves um par de câmeras calibradas. A snake-3D e representada espacialmente por uma B-spline que evolui sob as restricoes de forcas externas ao contorno ativo e internas a este. As forcas externas sao obtidas a partir dos pares de imagens que capturam a evolucao do arco eletrico, enquanto que as forcas internas sao intrinsecas ao contorno ativo e determinadas pela tensao entre pontos de controle adjacentes. Em relacao as outras abordagens para recuperacao da geometria 3D de arcos eletricos, o modelo aqui proposto e independente da determinacao de pontos homologos e de um posicionamento especifico de câmeras alem de propiciar o rastreio do arco eletrico levando em consideracao a dependencia temporal entre pares consecutivos de quadros em dois videos. Para fins de avaliacao foram realizados experimentos sobre imagens sinteticas obtidas a partir da simulacao de um sistema de aquisicao de imagens, bem como experimentos com imagens de arcos eletricos reais produzidos no CEPEL. Os resultados obtidos foram considerados aceitaveis, demonstrando o potencial da abordagem apresentada.